U.S. patent application number 15/577380 was filed with the patent office on 2018-06-21 for structure for fluid flowback control decision making and optimization.
The applicant listed for this patent is Halliburton Energy Services, Inc.. Invention is credited to Jason D. Dykstra, Qiuying Gu, Zhijie Sun.
Application Number | 20180171769 15/577380 |
Document ID | / |
Family ID | 57834995 |
Filed Date | 2018-06-21 |
United States Patent
Application |
20180171769 |
Kind Code |
A1 |
Gu; Qiuying ; et
al. |
June 21, 2018 |
Structure For Fluid Flowback Control Decision Making And
Optimization
Abstract
Methods and systems are presented in this disclosure for
evaluating whether to apply fluid flowback during a fracture
closure stage of a hydraulic fracturing operation of a reservoir
formation. Information collected prior to the fracture closure
stage of the hydraulic fracturing operation can be first gathered.
Based on the collected information, it can be determined whether to
perform fluid flowback during the fracture closure stage following
a treatment stage of the fracturing operation. Based on the
determination, a rate of the fluid flowback can be adjusted and
optimized in real-time during the fracture closure stage.
Inventors: |
Gu; Qiuying; (Humble,
TX) ; Dykstra; Jason D.; (Spring, TX) ; Sun;
Zhijie; (Spring, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Halliburton Energy Services, Inc. |
Houston |
TX |
US |
|
|
Family ID: |
57834995 |
Appl. No.: |
15/577380 |
Filed: |
July 17, 2015 |
PCT Filed: |
July 17, 2015 |
PCT NO: |
PCT/US2015/041012 |
371 Date: |
November 28, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
E21B 49/008 20130101;
G06F 30/20 20200101; E21B 43/267 20130101; E21B 2200/22
20200501 |
International
Class: |
E21B 43/267 20060101
E21B043/267; E21B 49/00 20060101 E21B049/00; G06F 17/50 20060101
G06F017/50 |
Claims
1. A computer-implemented method for performing fluid flowback
control, the method comprising: obtaining information collected
prior to a fracture closure stage of a fracturing operation of a
formation; determining, based on the information, whether to
perform fluid flowback during the fracture closure stage following
a treatment stage of the fracturing operation; and adjusting, based
on the determination, a rate of the fluid flowback during the
fracture closure stage.
2. The method of claim 1, wherein: the information is selected from
the group consisting of formation information gained prior to the
treatment stage, time trajectories of system inputs during the
treatment stage, measurements obtained during the treatment stage,
and system parameters estimated based on the measurements; or the
determination comprises at least one of a pattern-recognition-based
determination, or a model-based determination.
3. (canceled)
4. The method of claim 2, wherein the pattern-recognition-based
determination comprises: obtaining a first set of well fracturing
system data of at least one of features and measured behavior of a
well fracturing system for which the fracturing operation is
initiated; comparing the first set of data with a second set of
well fracturing system data of completed fracturing operations or
with a classification rule resulting from the second set of well
fracturing system data; and initiating, based on the comparison,
the adjustment of the rate of the fluid flowback during the
fracture closure stage.
5. The method of claim 4, wherein the comparison comprises:
applying supervised learning classification to predict, based on
the second set of data, whether the fluid flowback prevents
proppant degradation associated with the fracturing operation.
6. The method of claim 2, wherein the model-based determination
comprises: creating a model of a predicted well fracturing system
behavior based on measurements obtained during the treatment stage
of the fracturing operation of the formation; and using the model
of the predicted well fracturing system behavior and a user-defined
objective to select the rate of the fluid flowback that optimizes
the user-defined objective.
7. The method of claim 6, further comprising: initiating the
adjustment of the rate of the fluid flowback during the fracture
closure stage, if the selected rate of the fluid flowback is
greater than zero.
8. The method of claim 2, wherein the pattern-recognition-based
determination based on supervised learning classification
comprises: adding, to a set of classifier training data, feature
data extracted from a historical database related to completed
fracturing operations; extracting features from the set of
classifier training data; training a classifier to predict whether
to perform the fluid flowback during the fracture closure stage,
based on the extracted features and identified classes related to
the feature data, the identified classes comprise recommendation
for fluid flowback associated with the completed fracturing
operations; and executing the classifier using a set of features
describing the treatment stage of the fracturing operation to
determine whether to perform the fluid flowback during the fracture
closure stage.
9. The method of claim 2, wherein the model-based determination
comprises: obtaining measurements from the initiated fracturing
operation; filtering the measurements to remove a noise; estimating
and updating unmeasured system states and model parameters based on
the filtered measurements; and determining, based on the updated
system states and model parameters, a sequence of changes in the
rate of the fluid flowback over a predefined time period that
optimize a user-defined objective.
10. The method of claim 9, wherein the user-defined objective
comprises minimizing a predicted amount of proppant degradation
during the fracture closure stage of the fracturing operation.
11. A system for performing fluid flowback control, the system
comprising: at least one processor; and a memory coupled to the
processor having instructions stored therein, which when executed
by the processor, cause the processor to perform functions,
including functions to: obtain information collected prior to a
fracture closure stage of a fracturing operation of a formation;
determine, based on the information, whether to perform fluid
flowback during the closure stage following a treatment stage of
the fracturing operation; and adjust, based on the determination, a
rate of the fluid flowback during the fracture closure stage.
12. The system of claim 11, wherein: the information is selected
from the group consisting of formation information gained prior to
the treatment stage, time trajectories of system inputs during the
treatment stage, measurements obtained during the treatment stage,
and system parameters estimated based on the measurements; or the
determination comprises at least one of a pattern-recognition-based
determination, or a model-based determination.
13. (canceled)
14. The system of claim 12, wherein the functions for the
pattern-recognition-based determination performed by the processor
include functions to: obtain a first set of well fracturing system
data of at least one of features and measured behavior of a well
fracturing system for which the fracturing operation is initiated;
compare the first set of data with a second set of well fracturing
system data of completed fracturing operations or with a
classification rule resulting from the second set of well
fracturing system data; and initiate, based on the comparison, the
adjustment of the rate of the fluid flowback during the fracture
closure stage.
15. The system of claim 14, wherein the functions performed by the
processor include functions to: apply supervised learning
classification to predict, based on the second set of data, whether
the fluid flowback prevents proppant degradation associated with
the fracturing operation.
16. The system of claim 12, wherein the functions for the
model-based determination performed by the processor include
functions to: create a model of a predicted well fracturing system
behavior based on measurements obtained during the treatment stage
of the fracturing operation of the formation; and use the model of
the predicted well fracturing system behavior and a user-defined
objective to select the rate of the fluid flowback that optimizes
the user-defined objective.
17. The system of claim 12, wherein the functions for the
pattern-recognition-based determination performed by the processor
include functions to: add, to a set of classifier training data,
feature data extracted from a historical database related to
completed fracturing operations; extract features from the set of
classifier training data; train a classifier to predict whether to
perform the fluid flowback during the fracture closure stage, based
on the extracted features and identified classes related to the
feature data, the identified classes comprise recommendation for
fluid flowback associated with the completed fracturing operations;
and execute the classifier using a set of features describing the
treatment stage of the fracturing operation to determine whether to
perform the fluid flowback during the fracture closure stage.
18. The system of claim 12, wherein the functions for the
model-based determination performed by the processor include
functions to: obtain measurements from the initiated fracturing
operation; filter the measurements to remove a noise; estimate and
update unmeasured system states and model parameters based on the
filtered measurements; and determine, based on the updated system
states and model parameters, a sequence of changes in the rate of
the fluid flowback over a predefined time period that optimize a
user-defined objective.
19. A computer-readable storage medium having instructions stored
therein, which when executed by a computer cause the computer to
perform a plurality of functions, including functions to: obtain
information collected prior to a fracture closure stage of a
fracturing operation of a formation; determine, based on the
information, whether to perform fluid flowback during the fracture
closure stage following a treatment stage of the fracturing
operation; and adjust, based on the determination, a rate of the
fluid flowback during the fracture closure stage.
20. The computer-readable storage medium of claim 19, wherein the
instructions further perform functions to: obtain a first set of
well fracturing system data of at least one of features and
measured behavior of a well fracturing system for which the
fracturing operation is initiated; compare the first set of data
with a second set of well fracturing system data of completed
fracturing operations or with a classification rule resulting from
the second set of well fracturing system data; and initiate, based
on the comparison, the adjustment of the rate of the fluid flowback
during the fracture closure stage.
21. A method for performing a hydraulic fracturing operation
comprising: initiating injection of a fracturing fluid into a
formation via a wellbore in a treatment stage of a fracturing
operation utilizing a pump truck; prior to a fracture closure stage
of the fracturing operation following the treatment stage,
determining whether conditions exist in a well fracturing system
for implementation of fluid flowback procedures; upon a
determination that fluid flowback procedures should be implemented
in a well fracturing operation, determining an optimized flowback
rate for the well fracturing system based on a predetermined
objective; and operating the well fracturing system to achieve the
optimized flowback rate.
22. The method of claim 21, further comprising utilizing the pump
truck to control the rate of flowback from the wellbore.
23. (canceled)
24. (canceled)
Description
TECHNICAL FIELD
[0001] The present disclosure generally relates to a method for
controlling a hydraulic fracturing operation and, more
particularly, to a framework structure for fluid flowback control
and optimization during fracture closure.
BACKGROUND
[0002] Hydrocarbon-producing wells are often stimulated by
hydraulic fracturing treatments. In hydraulic fracturing
operations, a viscous fracturing fluid, which also functions as a
carrier fluid, is pumped into a producing formation zone during an
injection or treatment stage at a rate and pressure such that one
or more fractures are formed in the zone. Typically, particulates,
such as graded sand, suspended in a portion of the fracturing fluid
are then deposited in the fractures when the fracturing fluid is
converted to a thin fluid to be returned to the surface. These
particulate solids, or "proppant particulates," serve to prevent
the fractures from fully closing so that conductive channels are
formed through which produced hydrocarbons can flow. Once
fracturing has occurred, in a fracture closure stage, the pressure
of the injected fluid is decreased to below the closure pressure of
the formation.
[0003] One phenomenon that can occur during the fracture closure
stage is flowback, where proppant is transported out of the
fractures and formation, carried by the flowing formation fluids
and carrier fluid as the well is allowed to produce. Proppant
crushing after the fracturing treatment stage has ended can also
occur as the associated fracturing pressure is bled off, i.e., the
fracture closure stage, leading to the loss of fracture
conductivity as crushed proppant inhibits flow. Additionally, in
certain low permeability reservoirs, due to the characteristic low
leak-off rates of treatment fluids to the formation, a previously
suspended proppant may settle to the fracture bottom before it can
be trapped between fracture walls, if the fracture walls take too
much time to close.
[0004] Often times, it is necessary to balance these various
phenomenons. For example, by allowing proppant to flowback into the
wellbore with formation and treatment fluids, the amount of
undesired proppant settling may be decreased. However, in such
case, the amount of proppant loss from the formation fractures back
to the wellbore would potentially increase. Therefore, it is
desirable to optimize flowback, and to calculate a preferred
flowback rate of treatment fluids during fracture closure.
BRIEF DESCRIPTION OF THE DRAWINGS
[0005] Various embodiments of the present disclosure will be
understood more fully from the detailed description given below and
from the accompanying drawings of various embodiments of the
disclosure. In the drawings, like reference numbers may indicate
identical or functionally similar elements.
[0006] FIG. 1A is a diagram of an example well fracturing system
for applying a fracture treatment to a subterranean formation,
according to certain embodiments of the present disclosure.
[0007] FIG. 1B is a block diagram of a structure of a fluid
flowback control method, according to certain embodiments of the
present disclosure.
[0008] FIG. 2 is a block diagram of an expert system for fluid
flowback control decision making, according to certain embodiments
of the present disclosure.
[0009] FIG. 3 is a block diagram of a pattern-recognition-based
fluid flowback control necessity detection method, according to
certain embodiments of the present disclosure.
[0010] FIG. 4 is a block diagram of a model-based fluid flowback
control necessity detection method, according to certain
embodiments of the present disclosure.
[0011] FIG. 5 is a graph of an example pattern classification on a
fluid leak-off rate and an average fracture width, according to
certain embodiments of the present disclosure.
[0012] FIG. 6 is a flow chart of a method for the fluid flowback
control and optimization, according to certain embodiments of the
present disclosure.
[0013] FIG. 7 is a block diagram of an illustrative computer system
in which embodiments of the present disclosure may be
implemented.
DETAILED DESCRIPTION
[0014] Embodiments of the present disclosure relate to a framework
for optimizing treatment fluid flowback during a fracture closure
stage of a hydraulic fracturing operation, and thereafter,
controlling the flowback to achieve a desired objective. While the
present disclosure is described herein with reference to
illustrative embodiments for particular applications, it should be
understood that embodiments are not limited thereto. Other
embodiments are possible, and modifications can be made to the
embodiments within the spirit and scope of the teachings herein and
additional fields in which the embodiments would be of significant
utility.
[0015] In the detailed description herein, references to "one
embodiment," "an embodiment," "an example embodiment," etc.,
indicate that the embodiment described may include a particular
feature, structure, or characteristic, but every embodiment may not
necessarily include the particular feature, structure, or
characteristic. Moreover, such phrases are not necessarily
referring to the same embodiment. Further, when a particular
feature, structure, or characteristic is described in connection
with an embodiment, it is submitted that it is within the knowledge
of one skilled in the art to implement such feature, structure, or
characteristic in connection with other embodiments whether or not
explicitly described. It would also be apparent to one skilled in
the relevant art that the embodiments, as described herein, can be
implemented in many different embodiments of software, hardware,
firmware, and/or the entities illustrated in the figures. Any
actual software code with the specialized control of hardware to
implement embodiments is not limiting of the detailed description.
Thus, the operational behavior of embodiments will be described
with the understanding that modifications and variations of the
embodiments are possible, given the level of detail presented
herein.
[0016] The foregoing disclosure may repeat reference numerals
and/or letters in the various examples. This repetition is for the
purpose of simplicity and clarity and does not in itself dictate a
relationship between the various embodiments and/or configurations
discussed. Further, spatially relative terms, such as "beneath,"
"below," "lower," "above," "upper," "uphole," "downhole,"
"upstream," "downstream," and the like, may be used herein for ease
of description to describe one element or feature's relationship to
another element(s) or feature(s) as illustrated in the figures. The
spatially relative terms are intended to encompass different
orientations of the apparatus in use or operation in addition to
the orientation depicted in the figures. For example, if the
apparatus in the figures is turned over, elements described as
being "below" or "beneath" other elements or features would then be
oriented "above" the other elements or features. Thus, the
exemplary term "below" may encompass both an orientation of above
and below. The apparatus may be otherwise oriented (rotated 90
degrees or at other orientations) and the spatially relative
descriptors used herein may likewise be interpreted
accordingly.
[0017] Illustrative embodiments and related methods of the present
disclosure are described below in reference to FIGS. 1-7 as they
might be employed for performing fluid flowback control and
optimization during a fracture closure stage of a hydraulic
fracturing operation. Such embodiments and related methods may be
practiced, for example, using a computer system as described
herein. Other features and advantages of the disclosed embodiments
will be or will become apparent to one of ordinary skill in the art
upon examination of the following figures and detailed description.
It is intended that all such additional features and advantages be
included within the scope of the disclosed embodiments. Further,
the illustrated figures are only exemplary and are not intended to
assert or imply any limitation with regard to the environment,
architecture, design, or process in which different embodiments may
be implemented.
[0018] An intelligent decision making method, referred to as an
expert system, is presented in this disclosure for evaluating the
necessity of applying forced flowback of a treatment fluid during a
fracture closure stage of a hydraulic fracturing operation. The
evaluation may be based at least in part upon local formation
properties and a system behavior during a fracture treatment stage
preceding the fracture closure stage. Furthermore, an optimization
and control structure, referred to as a flowback control framework,
is provided for real-time adjustment of a fluid flowback rate in
order to effect a desired fracture closure time and propped
fracture geometry. With the flowback control framework presented in
this disclosure, a user-defined objective function may be
optimized. For example, in embodiments, the user-defined objective
function may be related to maximizing an expected production over a
well lifetime. In other embodiments, the user-defined objective
function may be related to minimizing effects of proppant crushing,
settling, and/or proppant flowback into a wellbore on the final
fracture conductivity.
[0019] In one or more embodiments, the decision making expert
system presented in this disclosure may be configured to determine
whether or not to flowback a treatment fluid during fracture
closure. If the fluid flowback is deemed necessary (e.g.,
determined by the expert system), an optimization and control
framework may be configured to adjust fluid flowback parameters.
Such parameters may include pressure and/or flow rate. In one or
more embodiments, adjustments to the fluid flowback rate may be
made in real-time during the fracture closure in order to take
advantage of updated system measurements obtained during this
operation.
[0020] FIG. 1A is a diagram of an example well fracturing system 10
for applying a fracture treatment to a subterranean formation 12.
Fracture treatments may be used, for example, to form or propagate
fractures in a rock layer by injecting pressurized fluid. The
fracture treatment may enhance or otherwise influence production of
petroleum, natural gas, coal seam gas, or other types of reservoir
resources. Fracture treatments may be used for other purposes. The
example well fracturing system 10 includes a reservoir 18 in the
subterranean formation 12 and an injection system 14 that applies
fracturing fluid 16 from a fracturing fluid source 17 to the
reservoir 18. The injection system 14 includes control trucks 20,
pump trucks 22, a wellbore 24, a working string 26 and other
equipment. In the example shown in FIG. 1A, the pump trucks 22, the
control trucks 20 and other related equipment are above the surface
28, and the wellbore 24, the working string 26, and other equipment
are beneath the surface 28. An injection system can be configured
as shown in FIG. 1A or in a different manner, and may include
additional or different features as appropriate. The injection
system 14 may be deployed in any suitable environment, for example,
via skid equipment, a marine vessel, sub-sea deployed equipment, or
other types of equipment.
[0021] The wellbore 24 can include both vertical and horizontal
sections, such as shown in FIG. 1A, and the fracturing fluid 16 is
applied to the reservoir 18, which resides near the wellbore 24.
Generally, a wellbore may include horizontal, vertical, slant,
curved, and other types of wellbore geometries and orientations,
and the fracture treatment may generally be applied to any portion
of a subterranean formation 12. The wellbore 24 can include a
casing that is cemented or otherwise secured to the wellbore wall.
The wellbore 24 can be uncased or include uncased sections.
Perforations can be formed in the casing to allow fracturing fluids
and/or other materials to flow into the reservoir 18. Perforations
can be formed using shape charges, a perforating gun, and/or other
tools.
[0022] The pump trucks 22 may include mobile vehicles, immobile
installations, skids, hoses, tubes, fluid tanks or reservoirs,
blenders, pumps, valves, and/or other suitable structures and
equipment. The pump trucks 22 can communicate with the control
trucks 20, for example, by a communication link 30. The pump trucks
22 are coupled via a wellhead 21 to the working string 26 to
communicate the fracturing fluid 16 into the wellbore 24. The
working string 26 may include coiled tubing, sectioned pipe, and/or
other structures that communicate fluid through the wellbore 24.
The working string 26 can include flow control devices, bypass
valves, ports, and or other tools or well devices that control the
flow of fluid from the interior of the working string 26 into the
reservoir 18.
[0023] The fracturing fluid 16 can include any appropriate fluid or
fluid composition. For example, the fracturing fluid 16 can include
hydraulic fracturing fluids, chemical treatment fluids, and other
types of fluids. The fracturing fluid 16 may include proppant-laden
fluids, thin fluids, gels, foams, additives, water, slurry,
liquids, gases or any suitable combination. The techniques
described here may be used to model the flow of fluids that are
injected for purposes other than fracturing. As such, the
fracturing fluid 16 may generally include fluids injected for
applying fracture treatments, chemical treatments, heat treatments,
or any suitable combination of these and other fluids. For
illustrative purposes only a proppant source 19 is shown in flow
communication with pump truck 22.
[0024] The control trucks 20 can include mobile vehicles, immobile
installations, and/or other suitable structures. Control truck 20
may be integrated with pump truck 22, and may be coupled to the
wellhead 21. The control trucks 20 can control and/or monitor the
injection treatment. For example, the control trucks 20 may include
communication links 30 that allow the control trucks 20 to
communicate with tools, sensors, and/or other devices installed in
the wellbore 24 or at the surface, such as sensors 25. The control
trucks 20 may receive data from, or otherwise communicate with, a
computing system 32 that models one or more aspects of the fracture
treatment. In addition, the control trucks 20 may include
communication links that allow the control trucks 20 to communicate
with the pump trucks 22 and/or other systems. The control trucks 20
may include an injection control system that controls the flow of
the fracturing fluid 16 into the reservoir 18. For example, the
control trucks 20 may monitor and/or control the density, volume,
flow rate, flow pressure, location, proppant, flowback and/or other
properties of the fracturing fluid 16 injected into the reservoir
18.
[0025] The reservoir 18 can include a fracture network 34, as shown
in FIG. 1A. Some or all of the fracture network 34 can be selected
for analysis by the computing system 32. For example, given an area
(e.g., surrounding the wellbore 24), a subset of the area (e.g.,
defined by a selected width, depth, and length) or all of the area
can be modeled by the computing system 32.
[0026] In one aspect of operation, the injection system 14 applies
a fracture treatment to the reservoir 18. The control truck 20
controls and monitors the pump truck 22, which pumps the fracturing
fluid 16 through the work string 26, into the wellbore 24, and
subsequently into the reservoir 18. The fracturing fluid 16 can be
injected at a pressure that fractures the reservoir media in the
reservoir 18. Some aspects of the fracture treatment may be
selected, tuned, or otherwise parameterized based on information
provided by the computing system 32, in real time or based on prior
treatments (e.g., prior treatments in similar settings, etc.). For
example, the fracture treatment may be designed based or adjusted
in real time in part on computer simulations indicating a rate of
fracture fluid flowback from the reservoir 18.
[0027] FIG. 1B is a block diagram of a structure 100 of a fluid
flowback control method, according to certain embodiments of the
present disclosure. As illustrated in FIG. 1B, the structure 100 of
the fluid flowback control may comprise two main subsystems, an
expert system 102 and a flowback control framework 104. The expert
system 102 may be configured to evaluate (e.g., before fracture
shut-in) the necessity of performing fluid flowback based upon one
or more inputs 106. Such inputs 106 may be information collected
before and during a treatment stage of a current hydraulic
fracturing operation. In one or more embodiments, the inputs 106
may be related to formation information gained prior to the current
treatment stage. In one or more other embodiments, the inputs 106
may comprise measurement information 106a obtained during the
fracture treatment. For example, the measurement information 106a
may be obtained by one or more sensors located in a wellbore (such
as sensors 25 located in wellbore 24 in FIG. 1A). Likewise, such
inputs 106 may be time trajectories of system inputs 106b during
the fracture treatment. For example, the time trajectories of
system inputs 106b may be information about changes of a fluid flow
rate over time during the fracture treatment (e.g., obtained by
flowmeters or sensors 25 at wellhead 21 of well fracturing system
10 in FIG. 1A and/or by pump sensors 25 coupled to pump trucks 22
in FIG. 1A), and/or information about changes over time during the
fracture treatment in concentration of proppant added to a
treatment fluid. Finally, inputs 106 may be related to formation
parameters, such as formation information (measured and/or
estimated) 106c, which may be estimated, in some embodiments, based
on measurement information 106a received from one or more sensors
(such as sensors 25 in FIG. 1A) deployed in a well fracturing
system that is the subject of proposed or active hydraulic
fracturing operations.
[0028] In one or more embodiments, an output 108 of the expert
system 102 may comprise a decision, as discussed in more detail
below, about the necessity of performing fluid flowback during a
fracture closure stage following the fracture injection or
treatment stage. If, based on the expert system output 108, the
fluid flowback is not required (e.g., determined at a decision
block 110), the fracture may be shut-in during the fracture closure
stage. In the case when the fluid flowback is warranted based on
the expert system output 108, optimization of a fluid flowback rate
may be initiated through the framework 104. Such optimization may
be carried out at a discreet point in time, such as prior to the
fracture closure stage, or may be carried out continuously in
real-time and used to control flowback throughout the fracture
closure stage of the hydraulic fracturing operation.
[0029] FIG. 2 is a block diagram 200 of an expert system for fluid
flowback control decision making, according to certain embodiments
of the present disclosure. As illustrated in FIG. 2, an expert
system 202 (e.g., which may correspond to the expert system 102
from FIG. 1B) may utilize, separately or in parallel, two different
methods for detecting the necessity of fluid flowback control
during a fracture closure stage of a current fracturing operation,
namely a pattern-recognition-based detection method 204 and a
model-based detection method 206. In one or more embodiments, the
pattern-recognition-based detection method 204 may determine
whether the fluid flowback control is required based upon
similarities of features and/or measured behavior data of a current
(or proposed) well fracturing system (such as system 10 in FIG. 1A)
compared to a historical database of features and/or measured data
from well fracturing systems of completed or past fracturing
operations, and whether, proppant bank degradation occurred in the
completed fracturing operations. Such well fracturing system data
may relate to a formation itself, equipment utilized (or proposed
to be utilized, as the case may be) in a fracturing operation,
information related to any of the forgoing obtained by sensors and
the response of any of the foregoing. For example, the
pattern-recognition-based detection 204 may determine that proppant
degradation occurred in completed jobs having historical data that
is similar to a pattern of features and measured behavior of the
current job. In such case, proppant degradation is deemed likely to
occur (e.g., established at a decision block 208), and the expert
system 202 and the pattern-recognition-based detection 204 may
output (e.g., through a decision block 210) a decision 212 to
initiate real-time control of a fluid flowback rate during the
fracture closure stage of the fracturing operation.
[0030] As further illustrated in FIG. 2, the model-based detection
method 206 of the expert system 202 may be operated separately or
in parallel with the pattern-recognition-based detection method 204
to determine whether fluid flowback during fracture closure should
be implemented. In one or more embodiments, the model-based
detection method 206 may be carried out by (1) creating or updating
a model of a predicted fracture system behavior (i.e., a fracture
closure model) through the use of measurements obtained during a
treatment stage preceding fracture closure in order to select an
appropriate closure model structure and estimate model parameters
and states; and (2) using, within an optimization program, the
closure model along with a user-selected objective (e.g., related
to a final condition of a closed fracture) to select a fluid
flowback rate 214 (the fluid flowback rate q.sub.b) that optimizes
the user-selected objective. If the predicted optimal fluid
flowback rate q.sub.b.sup.opt is greater than zero (e.g.,
determined at a decision block 216), then the expert system 202 and
the model-based detection 206 may output (e.g., through the
decision block 210) decision 212 to initiate real-time control of
the fluid flowback rate during the fracture closure stage. In other
embodiments, if the pattern-recognition-based detection 204
determines that proppant degradation is unlikely and the
model-based detection 206 determines that a fluid flowback rate of
zero (i.e., no flowback) is optimal, then the expert system 202 may
decide not to perform real-time control of the fluid flowback rate
during the fracture closure. In yet other embodiments, if the
pattern-recognition-based detection 204 determines that proppant
degradation is likely and the model-based detection 206 determines
that the fluid flowback rate of zero is optimal (i.e., the
pattern-recognition-based detection 204 and the model-based
detection 206 do not agree on the necessity to perform fluid
flowback), the expert system 202 may still initiate real-time
control of the fluid flowback rate during the fracture closure
stage. Similarly, if the pattern-recognition-based detection 204
determines that proppant degradation is unlikely and the
model-based detection 206 determines that the fluid flowback rate
greater than zero is optimal, the expert system 202 may also
initiate real-time control of the fluid flowback rate during the
fracture closure stage.
[0031] For some embodiments of the present disclosure, two types of
classification methods can be used for the
pattern-recognition-based detection method 204: supervised learning
and unsupervised learning. In one or more embodiments, the
supervised learning classification method may be used as the
pattern-recognition-based method to predict, based on historical
data from completed fracturing operations, whether fluid flowback
would prevent proppant degradation. Hence, a classifier created
according to the supervised learning classification method may
place the current fracturing system into one of two possible
classes, i.e., the "fluid flowback recommended" class and the
"fluid flowback not recommended" class.
[0032] FIG. 3 is a block diagram 300 of a pattern-based fluid
flowback control necessity detection method based on the supervised
learning classification, according to certain embodiments of the
present disclosure. For example, the pattern-based fluid flowback
control method illustrated in FIG. 3 may correspond to the
pattern-recognition-based detection method 204 of the expert system
200 illustrated in FIG. 2. Before classification of the current
fracturing system is attempted, a classifier 302 may be created
(e.g., within a classifier design block 304), according to a
particular supervised learning classification method chosen. In one
or more embodiments, the classifier 302 may be designed (e.g.,
within the classifier design block 304) based on training data,
which may be historical data sets 306 collected from completed
fracturing jobs. The training data (e.g., the historical data sets
306) may be reduced (e.g., within a feature extraction block 308)
into a set of features 310, which may represent basic units that
pattern classification techniques operate upon. A feature can be
any quality that can be used to describe a member of a data set
being classified. For example, features can include measured
quantities, model parameters, and/or choices made during a
fracturing operation.
[0033] For data from a completed fracturing job to be useful as
training data, classification of that completed fracturing job may
need to be known. There are two possible classes, i.e., the "fluid
flowback recommended" class and the "fluid flowback not
recommended" class. In one or more embodiments, the class may be
chosen based on an opinion of an expert familiar with one or more
fracturing jobs utilized as part of the evaluation set. In these
historical fracturing jobs, fluid flowback may or may not have been
conducted. For example, if the fluid flowback was not conducted and
a well was shut-in for fracture closure, the recommendation of
whether or not fluid flowback should have occurred can be made with
the benefit of hindsight based on whether proppant crushing and/or
proppant flowback were observed during cleanup and/or production.
On the other hand, if fluid flowback was implemented in the
historical fracturing jobs in the evaluation set, the posterior
recommendation may be based on an expert opinion of whether or not
fluid flowback significantly aided in prevention of proppant
degradation.
[0034] For each set of historical data describing a particular
fracturing operation, if the recommendation on fluid flowback can
be determined (e.g., either "fluid flowback recommended" or "fluid
flowback not recommended"), this historical data can be added to
the set of classifier training data 306. Then, the features 310 and
an identified class 312 may be extracted from this training data
306, and utilized by the classifier design block 304 in creating
the classifier 302.
[0035] Two different types of feature sources are presented in this
disclosure, i.e., direct feature sources and indirect feature
sources. In one or more embodiments, direct feature sources may
comprise formation parameters, such as Young's modulus, shear
modulus, leak-off coefficient, porosity and permeability. In one or
more embodiments, indirect feature sources (i.e., feature sources
obtained indirectly through various measurements) may comprise
records over time (time trajectories) of different variables that
can be manipulated, and measurements related to a fracturing
system. Time trajectories of manipulated variables refer to records
of system inputs, which may include, without limitation, records of
fluid injection rates, records of fluid flow pressures, records of
fluid volumes, records of fluid densities, or records of proppant
concentrations in treatment fluids. Fracturing system measurements
may include, without limitation, downhole pressures or
micro-seismic data. With a proper measurement filter structure, the
fracture length growth pattern over time may be estimated from the
micro seismic events.
[0036] In one or more embodiments, the indirect feature extraction
may comprise identification of one or more models to describe at
least one of the following: time-dependent manipulated variable,
state estimate, or measurement trajectories. For example, in an
embodiment of measurement trajectories, the concentration of
proppant added to a treatment fluid pumped downhole may be
described by the model:
C ( t ) = a 1 ( t - .tau. 1 t end - .tau. 1 ) a 2 , ( 1 )
##EQU00001##
where a.sub.1 and a.sub.2 are trajectory parameters or features
that describe the time trajectory of proppant concentration,
.tau..sub.1 is a time instant when a treatment stage starts, and
t.sub.end is a time instant when the treatment stage ends. In other
embodiments, a fitting polynomial model or time series models
between different available time trajectories may be implemented,
wherein the model parameters may be used as features. For example,
the AutoRegressive-Moving-Average model with eXogenous inputs
(i.e., ARMAX type model) may describe relation between a fracture
length L.sub.t and an injection rate q.sub.t at a given time
instant t such as:
L.sub.t=.gamma..sub.1q.sub.t-1+ . . .
+.gamma..sub.nq.sub.t-n+.delta..sub.1L.sub.t-1+ . . .
+.delta..sub.m+ce.sub.t, (2)
where .gamma..sub.i (i=1, . . . , n) and .delta..sub.j (j=1, . . .
, m) are model parameters, c is a constant coefficient and e.sub.t
is a white noise. The ARMAX type model may be used to generate
features from the model parameters .gamma..sub.i (i=1, . . . , n),
.delta..sub.j (j=1, . . . , m) and the constant coefficient c.
[0037] Following feature extraction and dimension reduction of
historical data, the next operation is designing classifier 302
(e.g., within the classifier design block 304). In one or more
embodiments, classifier 302 may be designed using, for example, the
support vector machine (SVM) method. The SVM-based classifier 302
may be trained to provide a level of performance based on a set of
feature data extracted from the historical database 306. Given the
other features, the SVM-based classifier 302 may be able to predict
whether or not fluid flowback was recommended in each case. In
embodiments, training of the classifier 302 may be carried out
offline, e.g., long before a current fracturing job. After design
of the classifier 302 is finalized, the classifier 302 may be used
on subsequent fracturing operations at the end of the treatment
stage. As illustrated in FIG. 3, data 314 from a current fracture
treatment may be reduced, within a feature extraction block 316,
into a set of features 318 describing the current fracture
treatment and the fracture system behavior. Then, the classifier
302 may be executed using the set of features 318 to determine
whether the current fracturing system belongs to the "fluid
flowback recommended" class or the "fluid flowback not recommended"
class.
[0038] FIG. 4 is a block diagram of a fluid flowback control
framework 400 configured in accordance with the model-based
detection method 206 of the expert system 200 illustrated in FIG.
2, according to certain embodiments of the present disclosure. As
discussed, the model-based detection 206 may be applied to evaluate
the necessity of implementing fluid flowback (as opposed to
shutting in the wellbore during a fracture closure stage of a
hydraulic fracturing operation) from the model-simulation point of
view. In one or more embodiments, a model of a predicted fracture
system behavior (i.e., the fracture closure model) may include the
ability to predict the behavior of fracture fluid flow, the
fracture geometry, and/or the proppant transport during fracturing
closure. In order to achieve a better prediction of fracture system
behavior, parameters of the fracture closure model (e.g., a
leak-off coefficient, formation properties, and the like) may be
estimated during fracture treatment using measurements received
during the fracture treatment stage of a fracturing operation. The
parameterized fracture closure model may be then utilized to
predict a fluid flowback rate that would optimize a final
conductivity of a fracture. If the predicted optimal fluid flowback
rate is greater than zero, then the model-based fluid flowback
control may be initiated during the fracture closure stage of the
fracturing operation.
[0039] The flowchart 400 illustrated in FIG. 4 shows one potential
implementation of the model-based control framework. A hydraulic
fracturing system, such as injection system 14 shown in FIG. 1A,
under control may comprise the following components: fracturing
process 402, which may involve a surface equipment, such as pump
truck 22 shown in FIG. 1A and any related hoses, tubes, fluid tanks
or reservoirs, blenders, pumps, valves, the well and fracture, and
sensors, such as sensors 25 shown in FIG. 1A, for measuring the
fracturing process; measurements (sensor readings) 404 produced
during the fracturing process 402 by the sensors that may be
recorded digitally; a module 406 for system state and model
parameter estimation that may be implemented on a computer system;
state and parameter estimates 408 produced by the estimator 406; a
model-based optimizer and controller 410 (e.g., implemented by
software on the computer system); a flowback simulation model 412
(e.g., integrated within the model-based optimizer and controller
410) used to predict future behavior of the fracturing system
(e.g., implemented on the computer system). Furthermore, a
component 414 of the model-based control framework 400 may comprise
a user-defined objective, which may be provided to the optimizer
and controller 410. For example, the user-defined objective 414 may
be to minimize a predicted amount of proppant that will be either
crushed, settled, or lost to a wellbore during fracture closure. As
illustrated in FIG. 4, an output 416 of the optimizer and
controller 410 may be a desired (optimized) rate of fluid flowback
from the fracture to the wellbore.
[0040] In one or more embodiments, the measurements (e.g., sensor
readings) 404 from the fracturing process 402 may be fed into the
system state and model parameter estimator module 406. For example,
the measurements 404 may include at least one of a proppant
concentration of a treatment fluid flowed back to a surface, a
wellbore pressure, or injection rates, concentrations or pressures.
In an embodiment, after being fed to the estimator module 406, the
measurements 404 may be also filtered to remove the effects of
noise. Then, the filtered measurements 404 may be mutually combined
(e.g., within the estimator module 406) and used to estimate other
unmeasured system states 408. In one or more embodiments, the state
estimation technique implemented within the estimator module 406
may be based on particle filtering. For example, the particle
filtering may utilize a nonlinear system model to produce an
ensemble of state estimates 408, calculate a weight associated with
each state estimate within the ensemble based on its possibility to
generate each received measurement, and then compute a preferred
state estimate based on the weighted ensemble of state
estimates.
[0041] In one or more embodiments, model parameters 408 may be
estimated by the estimator module 406 (e.g., simultaneously with
the state estimation) using the same particle filtering mechanism.
Over time, adaptation of the estimated model parameters 408 may
lead to a better ability of the model to predict the future
response of the fracturing system to changes in a fluid flowback
rate. In an embodiment, the update of system state and model
parameter estimates 408 may be conducted at the same temporal speed
as refreshment of the measurements 404 associated with the
fracturing process 402. The updated system state and model
parameter estimates 408 may be then used inside the optimizer and
controller 410 to predict future system behavior over a predefined
time horizon. The optimizer and controller 410 may then compute a
preferred sequence of changes in the fluid flowback rate that would
optimize the objective function 414. The first computed change in
the fluid flowback rate then may be implemented by the fracturing
system. In one or more embodiments, the operations may be repeated
at subsequent controller time steps.
[0042] FIG. 5 is a graph 500 of an example pattern classification
on a fluid leak-off rate and an average fracture width, according
to certain embodiments of the present disclosure. The pattern
classification illustrated in FIG. 5 may be in accordance with the
pattern-recognition-based detection method based on supervised
learning classification illustrated in FIG. 3. In the example
illustrated in FIG. 5, the Kernel SVM method is chosen to generate
a nonlinear classifier (e.g., the classifier 302 of the
pattern-based fluid flowback control framework illustrated in FIG.
3). An average fracture width 502 and a leak-off coefficient (rate)
504 represent two features taken from a set of historical data
(e.g., the historical data 306 in FIG. 3), and used to train the
classifier (e.g., the classifier 302 in FIG. 3). As illustrated in
FIG. 5, training data can be divided into two groups: training data
506 belonging to a class "fluid flowback not recommended" and
training data 508 belonging to another class "fluid flowback
recommended". The nonlinear classifier (e.g., the classifier 302 in
FIG. 3) created from the training data 506 and 508 can be used to
determine whether data 510 from a current fracture job belongs to
the class "fluid flowback recommended" or to the other class "fluid
flowback not recommended" based upon its estimated average fracture
width 502 and leak-off coefficient 504. The determination of class
to which the current fracture data 510 belongs may be based on
which side of a classification (decision) boundary 512 the data
point 510 from the current fracture is located. In the example data
illustrated in FIG. 5, the current fracture data 510 is classified
as the class "fluid flowback recommended".
[0043] Due to the nature of the formation effect on the classifier
(e.g., the classifier 302 in FIG. 3), a reclassification may be
applied from one field to another, or from one zone to another. As
data are used for fluid flowback control, the reclassification may
be further automatically integrated into the classifier training
with known post job performance metrics. If there is a consistent
error in the classification model, depending on the severity, the
classifier may be scraped and relearned with the local field
training data. When this relearning is in process, a margin
boundary (e.g., margin boundaries 514 illustrated in FIG. 5) may
become the feedback term for an operator to understand the quality
of the classifier model. For example, once the margin boundary
(e.g., the margin boundaries 514) drops below a specified level
indicating the model distribution has a decreased standard
deviation, the margin boundary can again be used to control the
flowback system.
[0044] Discussion of an illustrative method of the present
disclosure will now be made with reference to FIG. 6, which is a
flow chart 600 of a method for performing fluid flowback control
and optimization, according to certain embodiments of the present
disclosure. The method begins at 602 by obtaining information
collected prior to a fracture closure stage of a fracturing
operation of a reservoir formation. At 604, based on the collected
information, it may be determined (e.g., by the expert system 102
in FIG. 1B and/or the expert system 202 in FIG. 2 by employing the
pattern-recognition-based detection method 204 and/or the
model-based detection method 206) whether to perform fluid flowback
during the fracture closure stage following a treatment stage of
the fracturing operation. At 606, based on the determination, a
rate of the fluid flowback may be adjusted (and optimized) during
the fracture closure stage.
[0045] FIG. 7 is a block diagram of an illustrative computing
system 700 (also illustrated in FIG. 1A as computing system 32) in
which embodiments of the present disclosure may be implemented
adapted for implementing the fluid flowback control in hydraulic
fracturing. For example, the operations of frameworks 100, 200, 300
and 400 from FIGS. 1B-4 and the operations of method 600 of FIG. 6,
as described above, may be implemented using the computing system
700. The computing system 700 can be a computer, phone, personal
digital assistant (PDA), or any other type of electronic device.
Such an electronic device includes various types of computer
readable media and interfaces for various other types of computer
readable media. As shown in FIG. 7, the computing system 700
includes a permanent storage device 702, a system memory 704, an
output device interface 706, a system communications bus 708, a
read-only memory (ROM) 710, processing unit(s) 712, an input device
interface 714, and a network interface 716.
[0046] The bus 708 collectively represents all system, peripheral,
and chipset buses that communicatively connect the numerous
internal devices of the computing system 700. For instance, the bus
708 communicatively connects the processing unit(s) 712 with the
ROM 710, the system memory 704, and the permanent storage device
702.
[0047] From these various memory units, the processing unit(s) 712
retrieves instructions to execute and data to process in order to
execute the processes of the subject disclosure. The processing
unit(s) can be a single processor or a multi-core processor in
different implementations.
[0048] The ROM 710 stores static data and instructions that are
needed by the processing unit(s) 712 and other modules of the
computing system 700. The permanent storage device 702, on the
other hand, is a read-and-write memory device. This device is a
non-volatile memory unit that stores instructions and data even
when the computing system 700 is off. Some implementations of the
subject disclosure use a mass-storage device (such as a magnetic or
optical disk and its corresponding disk drive) as the permanent
storage device 702.
[0049] Other implementations use a removable storage device (such
as a floppy disk, flash drive, and its corresponding disk drive) as
the permanent storage device 702. Like the permanent storage device
702, the system memory 704 is a read-and-write memory device.
However, unlike the storage device 702, the system memory 704 is a
volatile read-and-write memory, such a random access memory. The
system memory 704 stores some of the instructions and data that the
processor needs at runtime. In some implementations, the processes
of the subject disclosure are stored in the system memory 704, the
permanent storage device 702, and/or the ROM 710. For example, the
various memory units include instructions for computer aided pipe
string design based on existing string designs in accordance with
some implementations. From these various memory units, the
processing unit(s) 712 retrieves instructions to execute and data
to process in order to execute the processes of some
implementations.
[0050] The bus 708 also connects to the input and output device
interfaces 714 and 706. The input device interface 714 enables the
user to communicate information and select commands to the
computing system 700. Input devices used with the input device
interface 714 include, for example, alphanumeric, QWERTY, or T9
keyboards, microphones, and pointing devices (also called "cursor
control devices"). The output device interfaces 706 enables, for
example, the display of images generated by the computing system
700. Output devices used with the output device interface 706
include, for example, printers and display devices, such as cathode
ray tubes (CRT) or liquid crystal displays (LCD). Some
implementations include devices such as a touchscreen that
functions as both input and output devices. It should be
appreciated that embodiments of the present disclosure may be
implemented using a computer including any of various types of
input and output devices for enabling interaction with a user. Such
interaction may include feedback to or from the user in different
forms of sensory feedback including, but not limited to, visual
feedback, auditory feedback, or tactile feedback. Further, input
from the user can be received in any form including, but not
limited to, acoustic, speech, or tactile input. Additionally,
interaction with the user may include transmitting and receiving
different types of information, e.g., in the form of documents, to
and from the user via the above-described interfaces.
[0051] Also, as shown in FIG. 7, the bus 708 also couples the
computing system 700 to a public or private network (not shown) or
combination of networks through a network interface 716. Such a
network may include, for example, a local area network ("LAN"),
such as an Intranet, or a wide area network ("WAN"), such as the
Internet. Any or all components of the computing system 700 can be
used in conjunction with the subject disclosure.
[0052] These functions described above can be implemented in
digital electronic circuitry, in computer software, firmware or
hardware. The techniques can be implemented using one or more
computer program products. Programmable processors and computers
can be included in or packaged as mobile devices. The processes and
logic flows can be performed by one or more programmable processors
and by one or more programmable logic circuitry. General and
special purpose computing devices and storage devices can be
interconnected through communication networks.
[0053] Some implementations include electronic components, such as
microprocessors, storage and memory that store computer program
instructions in a machine-readable or computer-readable medium
(alternatively referred to as computer-readable storage media,
machine-readable media, or machine-readable storage media). Some
examples of such computer-readable media include RAM, ROM,
read-only compact discs (CD-ROM), recordable compact discs (CD-R),
rewritable compact discs (CD-RW), read-only digital versatile discs
(e.g., DVD-ROM, dual-layer DVD-ROM), a variety of
recordable/rewritable DVDs (e.g., DVD-RAM, DVD-RW, DVD+RW, etc.),
flash memory (e.g., SD cards, mini-SD cards, micro-SD cards, etc.),
magnetic and/or solid state hard drives, read-only and recordable
Blu-Ray.RTM. discs, ultra density optical discs, any other optical
or magnetic media, and floppy disks. The computer-readable media
can store a computer program that is executable by at least one
processing unit and includes sets of instructions for performing
various operations. Examples of computer programs or computer code
include machine code, such as is produced by a compiler, and files
including higher-level code that are executed by a computer, an
electronic component, or a microprocessor using an interpreter.
[0054] While the above discussion primarily refers to
microprocessor or multi-core processors that execute software, some
implementations are performed by one or more integrated circuits,
such as application specific integrated circuits (ASICs) or field
programmable gate arrays (FPGAs). In some implementations, such
integrated circuits execute instructions that are stored on the
circuit itself. Accordingly, the operations of frameworks 100, 200,
300 and 400 from FIGS. 1B-4 and the operations of method 600 of
FIG. 6, as described above, may be implemented using the computing
system 700 or any computer system having processing circuitry or a
computer program product including instructions stored therein,
which, when executed by at least one processor, causes the
processor to perform functions relating to these methods.
[0055] As used in this specification and any claims of this
application, the terms "computer", "server", "processor", and
"memory" all refer to electronic or other technological devices.
These terms exclude people or groups of people. As used herein, the
terms "computer readable medium" and "computer readable media"
refer generally to tangible, physical, and non-transitory
electronic storage mediums that store information in a form that is
readable by a computer.
[0056] Embodiments of the subject matter described in this
specification can be implemented in a computing system that
includes a back end component, e.g., as a data server, or that
includes a middleware component, e.g., an application server, or
that includes a front end component, e.g., a client computer having
a graphical user interface or a Web browser through which a user
can interact with an implementation of the subject matter described
in this specification, or any combination of one or more such back
end, middleware, or front end components. The components of the
system can be interconnected by any form or medium of digital data
communication, e.g., a communication network. Examples of
communication networks include a local area network ("LAN") and a
wide area network ("WAN"), an inter-network (e.g., the Internet),
and peer-to-peer networks (e.g., ad hoc peer-to-peer networks).
[0057] The computing system can include clients and servers. A
client and server are generally remote from each other and
typically interact through a communication network. The
relationship of client and server arises by virtue of computer
programs implemented on the respective computers and having a
client-server relationship to each other. In some embodiments, a
server transmits data (e.g., a web page) to a client device (e.g.,
for purposes of displaying data to and receiving user input from a
user interacting with the client device). Data generated at the
client device (e.g., a result of the user interaction) can be
received from the client device at the server.
[0058] It is understood that any specific order or hierarchy of
operations in the processes disclosed is an illustration of
exemplary approaches. Based upon design preferences, it is
understood that the specific order or hierarchy of operations in
the processes may be rearranged, or that all illustrated operations
be performed. Some of the operations may be performed
simultaneously. For example, in certain circumstances, multitasking
and parallel processing may be advantageous. Moreover, the
separation of various system components in the embodiments
described above should not be understood as requiring such
separation in all embodiments, and it should be understood that the
described program components and systems can generally be
integrated together in a single software product or packaged into
multiple software products.
[0059] Furthermore, the illustrative methods described herein may
be implemented by a system including processing circuitry or a
computer program product including instructions which, when
executed by at least one processor, causes the processor to perform
any of the methods described herein.
[0060] Referring back to FIG. 1A, computing system 32, such as
computing system 700 illustrated in FIG. 7, may be adapted for
implementing fluid flowback control decision making and
optimization as described in the present disclosure. For example,
during a hydraulic fracturing procedure, computing system 700 may
be configured to determine whether or not flowback of fracturing
fluid 16 during a fracture closure stage is desirable. If fluid
flowback is desired, the optimization and control framework
presented herein may be implemented by computing system 700 to
determine an optimal fluid flowback rate based on a particular set
of parameters. In one or more embodiments, adjustments to the fluid
flowback rate may be determined by computing system 700 in
real-time and implemented by injection system 14 during the
fracture closure stage to take advantage of updated system
measurements obtained during the fracturing operation. Furthermore,
computing system 700 may operate a fluid flow control module of the
working string 26, which may be configured to control the fluid
flowback during fracture closure as described in the present
disclosure.
[0061] Preventing proppant degradation during and after fracture
closure in the conventional manner is limited to physics-based
methods with a goal to either change the proppant property or the
fluid properties. The present disclosure differs from the
conventional approach by optimizing operational parameters of the
hydraulic fracturing procedure in order to minimize proppant
degradation. Advantages of the present disclosure include, but are
not limited to, dynamical real-time control of fluid flowback
during fracture closure, thus delivering improved performance of
the hydraulic fracturing operation, and optimization of
user-defined objectives.
[0062] A computer-implemented method for performing fluid flowback
control has been described in the present disclosure and may
generally include: obtaining information collected prior to a
fracture closure stage of a fracturing operation of a formation;
determining, based on the information, whether to perform fluid
flowback during the fracture closure stage following a treatment
stage of the fracturing operation; and adjusting, based on the
determination, a rate of the fluid flowback during the fracture
closure stage. Further, a computer-readable storage medium with
instructions stored therein has been described, instructions when
executed by a computer cause the computer to perform a plurality of
functions, including functions to: obtain information collected
prior to a fracture closure stage of a fracturing operation of a
formation; determine, based on the information, whether to perform
fluid flowback during the fracture closure stage following a
treatment stage of the fracturing operation; and adjust, based on
the determination, a rate of the fluid flowback during the fracture
closure stage. Further, a method for performing a hydraulic
fracturing operation has been described in the present disclosure
and may generally include: initiating injection of a fracturing
fluid into a formation via a wellbore in a treatment stage of a
fracturing operation utilizing a pump truck; prior to a fracture
closure stage of the fracturing operation following the treatment
stage, determining whether conditions exist in a well fracturing
system for implementation of fluid flowback procedures; upon a
determination that fluid flowback procedures should be implemented
in a well fracturing operation, determining an optimized flowback
rate for the well fracturing system based on a predetermined
objective; and operating the well fracturing system to achieve the
optimized flowback rate.
[0063] For the foregoing embodiments, the method or functions may
include any one of the following operations, alone or in
combination with each other: Selecting the information from the
group consisting of formation information gained prior to the
treatment stage, time trajectories of system inputs during the
treatment stage, measurements obtained during the treatment stage,
and system parameters estimated based on the measurements; The
determination comprises at least one of a pattern-recognition-based
determination, or a model-based determination; Obtaining a first
set of well fracturing system data of at least one of features and
measured behavior of a well fracturing system for which the
fracturing operation is initiated; Comparing the first set of data
with a second set of well fracturing system data of completed
fracturing operations or with a classification rule resulting from
the second set of well fracturing system data; initiating, based on
the comparison, the adjustment of the rate of the fluid flowback
during the fracture closure stage; Applying supervised learning
classification to predict, based on the second set of data, whether
the fluid flowback prevents proppant degradation associated with
the fracturing operation; Creating a model of a predicted well
fracturing system behavior based on measurements obtained during
the treatment stage of the fracturing operation of the formation;
Using the model of the predicted well fracturing system behavior
and a user-defined objective to select the rate of the fluid
flowback that optimizes the user-defined objective; Initiating the
adjustment of the rate of the fluid flowback during the fracture
closure stage, if the selected rate of the fluid flowback is
greater than zero; Adding, to a set of classifier training data,
feature data extracted from a historical database related to
completed fracturing operations; Extracting features from the set
of classifier training data; Training a classifier to predict
whether to perform the fluid flowback during the fracture closure
stage, based on the extracted features and identified classes
related to the feature data, the identified classes comprise
recommendation for fluid flowback associated with the completed
fracturing operations; Executing the classifier using a set of
features describing the treatment stage of the fracturing operation
to determine whether to perform the fluid flowback during the
fracture closure stage; Identifying one or more models describing
the at least one of the formation parameters, the manipulated
variables, or the fracturing system measurements; Obtaining
measurements from the initiated fracturing operation; Filtering the
measurements to remove a noise; Estimating and updating unmeasured
system states and model parameters based on the filtered
measurements; Determining, based on the updated system states and
model parameters, a sequence of changes in the rate of the fluid
flowback over a predefined time period that optimize a user-defined
objective; Utilizing the pump truck to control the rate of flowback
from the wellbore.
[0064] The features comprise at least one of: one or more formation
parameters, time trajectories of manipulated variables, or
fracturing system measurements; One or more formation parameters
comprise at least one of a Young's modulus, a shear modulus, a
leak-off coefficient, a porosity, or a permeability; The time
trajectories of manipulated variables are related to records of
system inputs comprising at least one of a fluid injection rate or
a proppant degradation; The fracturing system measurements comprise
at least one of a downhole pressure or micro seismic data with
information about a fracture length growth pattern over time; The
user-defined objective comprises minimizing a predicted amount of
proppant degradation during the fracture closure stage of the
fracturing operation; The second set of data comprises information
about proppant degradation related to the completed fracturing
operations; The user-defined objective is related to a final
condition of a fracture system after the fracture closure stage of
the fracturing operation.
[0065] Likewise, a system for performing fluid flowback control has
been described and include at least one processor and a memory
coupled to the processor having instructions stored therein, which
when executed by the processor, cause the processor to perform
functions, including functions to: obtain information collected
prior to a fracture closure stage of a fracturing operation of a
formation; determine, based on the information, whether to perform
fluid flowback during the closure stage following a treatment stage
of the fracturing operation; and adjust, based on the
determination, a rate of the fluid flowback during the fracture
closure stage. Further, a system for performing a hydraulic
fracturing operation has been described and may generally include a
pump truck; a fluid source; a proppant source; at least one sensor
disposed to measure a condition of a well fracturing system; and a
computer system with a software having instructions, the
instructions when executed by the computer system cause the
computer system to perform a plurality of functions, including
functions to: initiate injection of a fracturing fluid from the
fluid source into a formation via a wellbore in a treatment stage
of a fracturing operation utilizing the pump truck, the fracturing
fluid comprises a proppant from the proppant source; prior to a
fracture closure stage of the fracturing operation following the
treatment stage, determine, based on one or more measurements of
the at least one sensor, whether the condition of the well
fracturing system is for implementation of fluid flowback
procedures; upon a determination that the fluid flowback procedures
should be implemented in the hydraulic fracturing operation,
determine an optimized flowback rate for the well fracturing system
based on a predetermined objective; and generate an order to
operate the well fracturing system to achieve the optimized
flowback rate; the pump truck is further utilized to control the
rate of flowback from the wellbore.
[0066] As used herein, the term "determining" encompasses a wide
variety of actions. For example, "determining" may include
calculating, computing, processing, deriving, investigating,
looking up (e.g., looking up in a table, a database or another data
structure), ascertaining and the like. Also, "determining" may
include receiving (e.g., receiving information), accessing (e.g.,
accessing data in a memory) and the like. Also, "determining" may
include resolving, selecting, choosing, establishing and the
like.
[0067] As used herein, a phrase referring to "at least one of" a
list of items refers to any combination of those items, including
single members. As an example, "at least one of: a, b, or c" is
intended to cover: a, b, c, a-b, a-c, b-c, and a-b-c.
[0068] While specific details about the above embodiments have been
described, the above hardware and software descriptions are
intended merely as example embodiments and are not intended to
limit the structure or implementation of the disclosed embodiments.
For instance, although many other internal components of computer
system 700 are not shown, those of ordinary skill in the art will
appreciate that such components and their interconnection are well
known.
[0069] In addition, certain aspects of the disclosed embodiments,
as outlined above, may be embodied in software that is executed
using one or more processing units/components. Program aspects of
the technology may be thought of as "products" or "articles of
manufacture" typically in the form of executable code and/or
associated data that is carried on or embodied in a type of machine
readable medium. Tangible non-transitory "storage" type media
include any or all of the memory or other storage for the
computers, processors or the like, or associated modules thereof,
such as various semiconductor memories, tape drives, disk drives,
optical or magnetic disks, and the like, which may provide storage
at any time for the software programming.
[0070] Additionally, the flowchart and block diagrams in the
figures illustrate the architecture, functionality, and operation
of possible implementations of systems, methods and computer
program products according to various embodiments of the present
disclosure. It should also be noted that, in some alternative
implementations, the functions noted in the block may occur out of
the order noted in the figures. For example, two blocks shown in
succession may, in fact, be executed substantially concurrently, or
the blocks may sometimes be executed in the reverse order,
depending upon the functionality involved. It will also be noted
that each block of the block diagrams and/or flowchart
illustration, and combinations of blocks in the block diagrams
and/or flowchart illustration, can be implemented by special
purpose hardware-based systems that perform the specified functions
or acts, or combinations of special purpose hardware and computer
instructions.
[0071] The above specific example embodiments are not intended to
limit the scope of the claims. The example embodiments may be
modified by including, excluding, or combining one or more features
or functions described in the disclosure.
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